qtdocgallery fails to build from source, incorrect placement of #includes

The auto-generated sources from MOC for qtdocgallery are #include'd at the wrong location, inside namespaces as opposed to outside of the namespaces. As a result references to global namespace through the #include <memory> inside the autogenerated sources fail to be resolved correctly. This causes the build to fail with slightly cryptic error messages.

This bug is an attempt to get the original issue filed under the correct component with the right team members looking at it. See also:QTBUG-82690